1. Field of the Invention
The present invention relates to a lighting system for use in an image scanning device, particularly to a lighting system for an image scanning device, which combines a small volume with the capability to illuminate large images.
2. Description of Related Art
Light sources for image scanning devices are light-emitting diodes (LED), halogen lamps, tungsten-filament lamps, fluorescent lamps, and cold-cathode fluorescent lamps. A light source is chosen by virtue of its brightness, its price and the length of the area to be scanned at a time. If a line charge-coupled device (CCD) is used as the light detector in the scanning device, a fluorescent lamp or cold-cathode fluorescent lamp is employed. For the various formats of the scanned objects, the diameter and length of the fluorescent lamp or cold-cathode fluorescent lamp used are different. For example, size standards for fluorescent lamps are 4 w, 6 w, 8 w, 10 w, 20 w, and 40 w. In the same way, various sizes of cold-cathode fluorescent lamps are used, according to the lighting demands. If the scanned object is large, like A2, A1, or A0, a fluorescent lamp is generally of sufficient length.
As shown in FIGS. 8 and 9, the length of a conventional light source 1 for a scanning device has to cover the length of the scanned object 3 completely. Only then uniform lighting along the length of the scanned object is assured. Taking into account the glass material of the light source tube, the length and diameter of the light source have to be made even larger. So the light source takes up a large volume, preventing a compact design of the scanning device.